A waterfall display typically employs a submersible water pump to circulate water from a lower reservoir to an elevated surface from which the water cascades back toward the lower reservoir, thereby creating a simulated waterfall. Examples of such waterfall displays are disclosed in U.S. Pat. Nos. 3,901,439, 5,326,032 and 5,571,409. Such a waterfall display tends to be bulky and heavy because the pump is typically a submersible alternate-current (AC) powered pump that is large and unwieldy and requires a large reservoir for submersion therein. Submersible AC powered pumps are typically bulky and costly to manufacture because, due to their high operating voltage, they must meet stringent electrical shielding and/or insulation requirements to protect users and the pumps in an aqueous operating environment. The associated AC power cord also detracts from the aesthetics of the display as it is difficult to hide and route. Furthermore, the power cord, because of its limited length, restricts where the display may be located. As a result, the display can often not be placed at a desired location.
Accordingly, there is a need for small, low-cost battery or direct-current (DC) powered water pumps which have none of the aforementioned disadvantages. However, such DC powered water pumps must be energy efficient so as not to require users to frequently replace or recharge the batteries powering the motors. One way to increase the efficiency of a water pump is to reduce friction encountered by the rotating shaft of the motor. Because the motor must also be in a water tight chamber, a seal or gasket must be used to isolate the motor from the water. Such a gasket is mounted tightly about the shaft to isolate the motor from the aqueous environment in which the pump operates. The gasket must be dimensioned to apply sufficient sealing force against the motor shaft so as to prevent water from passing between the shaft and the gasket to reach the motor. However, such a tightly fitting gasket is a source of a considerable frictional load on the motor.
U.S. Pat. No. 4,021,150 discloses a battery powered water pump with a fluid flow directing device for directing fluid admitted through an inlet port to flow away from the motor shaft bearing toward the impeller of the pump. The fluid flow directing device consists of a conical section or a propeller mounted onto the motor shaft. However, in this device, all of the water being pumped flows past the motor shaft from the motor housing, thereby increasing the likelihood that water will leak into the motor housing to damage the motor.